Redox behavior of novel nickel and palladium complexes supported by trianionic non-innocent ligand containing β-diketiminate and phenol groups

A new type of nickel and palladium complexes with non-innocent β-diketiminate ligand having redox active phenol groups, 2,4-di-tert-butyl-6-(((1E,2E)-3-((3,5-di-tert-butyl-2-hydroxyphenyl) amino)-2-nitroallylidene)amino)phenol (LH₃, fully protonated form) have been developed, and the structure, physical properties, and reactivity of their one-electron and two-electron oxidized complexes, [M^II(L^•2-)] and [M^II(L^-)]⁺ (M = Ni^II or Pd^II) have been examined in detail. The two-electron oxidized forms of both complexes, [M^II(L^-)]⁺, exhibited hydrogen atom abstraction ability from 1,4-cyclohexadiene (CHD) comparable to its copper analog [Cu^II(L^-)]⁺ (Dalton Trans. 2013; 42: 2438-2444). The oneelectron oxidized form of palladium complex, [Pd^II(L^•2-)], was also found to oxidize CHD, whereas the nickel analog, [Ni^II(L^•2-)], exhibited photo-induced oxidation ability of CHD.